Undead Labs' open world game is more alive thanks to being "over-engineered."

On the surface, Undead Labs' State of Decay feels like a conventional open world game. The zombie apocalypse title is set for an XBLA release some time in 2013, and it features both an interface and third-person perspective familiar to anyone who played the likes of Grand Theft Auto, Crackdown, or Saints Row.

Surface-level differences between State of Decay and these other titles become readily apparent just a few minutes into a recent demo. Chief among them is the ability to fortify buildings into something “similar to a GTA safe house, but more robust” in the words of John Gronquist, one of the artists on the project. You have to fill in the limited number of build locations in each safe house with elements like gardens, sleeping areas, medical tents, and workshops, adding a real time strategy vibe to the proceedings. Players aren't tied to a single protagonist in State of Decay, either. When a character dies, the player takes control of one of the other survivors in their community to continue playing.

While those are important distinctions between State of Decay and other open world games, the most significant change might lie under the hood. During the demo, Gronquist referred to the game as having been “over-engineered.” He said Undead Labs performed an “extreme amount of engineering into the procedural simulation of the world... We wanted the world to be this organic thing where everything you did had a consequence to it.”

What does that mean, exactly? Undead Labs founder Jeff Strain and Creative Director James Phinney explained the world of State of Decay stays dynamic even when the player isn't watching.

“Instead of the world always being in a static state and always waiting for you to change the action, change the state of things, we said 'OK, what if we’re just simulating the state of the world and things are progressing?'” Phinney told Ars. When a player gathers survivors to join their community, for example, those survivors don’t just stand around while the player goes off to search for resources. “They’re out doing things all the time, too, trying to take care of the community, following the higher-level direction you set. And as we started to explore this feeling of having the world be alive and active, we just started to commit to it more and more.”

So unlike most open-world games, the world of State of Decay isn't just a backdrop for the narrative missions, but a simulation that is constantly progressing and changing. “Events are going on with or without you, and you choose how and whether to interact with them and that will modify the state of world, and if you ignore it that will also modify the state of the world,” said Strain.

One of the game's zombie types, called a Screamer, exemplifies this dynamism. Screamers have no arms and no lower jaw, so they can’t grab or bite the player, but their moans and screams can attract other zombies. Simulating natural Screamer behavior eventually and inevitably leads the Screamers to attract a huge zombie horde around them.

In other words, choosing whether or not to dispatch a Screamer now can have an effect on how many other zombies gather in that area later. Keeping a Screamer alive can turn previously safe areas quite dangerous, leading troubled survivors to call the player for help, requiring diversion of important resources. If State of Decay were constructed as a traditional single-player game, events like these might be hard-coded into the larger narrative. Instead, the game allows these kinds of events to emerge naturally from the simulation.

“[In] open world games, generally there’s this really strong distinction between the sense of freedom you have causing mayhem, and then the spots where there’s real content,” said Phinney. “There’s some storyline stuff that’s going to happen in a specific spot [in State of Decay], but what we did was try to as much as possible, and it is the majority I think of your play experience, have stuff be really heavily driven by what you’re encountering in the world and the state that you have left the world in.”

“Just a straight-up, more traditional open world zombie survival game would have been awesome, and would have been possible without this stuff,” Phinney continued. “But what we’ve found is, by going down this road, it’s a different experience entirely.”

And, again, that simulation doesn't stop when you stop playing. “When you stop playing the game for the day, conceptually the world is still running,” Strain said. “When you start up the game, what we effectively do is look at the amount of time that’s elapsed and forward the simulation by that amount of time. We’re careful not to punish you for that. You’re not gonna log back in after two weeks and find your bases destroyed and all your people are sick, but as a conceptual design platform we do say that time goes on, even when you’re not there.”

The kind of world a player returns to in a new State of Decay play session will depend largely on how the player’s behaved in the last play session. If you made sure your people had growing food and ammunition workshops and medical facilities in their safe house, they’ll be in good shape when you log back in. If you didn't plan for the future, though, you might find your survivors have gotten into an untenable situation.

Despite being what Gronquist called an “over-engineered” game, State of Decay seems to have just the right amount of engineering to create an open world game with some life to it. “Certainly we’re not doing anything gratuitously,” Phinney said when asked about this distinction. “We’re doing this because we had a vision of what this kind of experience could be, and we’re putting in all the core pieces to make that happen.”

“To address that point directly, I will say that it is over-engineered,” added Strain. “I mean, you are right, everything we’ve done has been expressly for the purpose of creating this living, breathing world…however, had our goal from the beginning been strictly to create an open-world sandbox zombie survival game, then there certainly would have been a much shorter and more direct path than the one we took. When we say it’s over-engineered, you hear us use this word 'simulation' all the time, the simulation itself is very robust, and far more robust than we would have needed to make it just to pull off that direct statement of the type of game we wanted to make right now.”

Undead Labs plans to supplement the single-player State of Decay with a massively-multiplayer experience in the same universe, code-named Class 4 (State of Decay was previously known as Class 3). This companion game helped motivate the creation of the robust simulation.

“We very much have been of a mind that with everything we’re doing in State of Decay to look at how it sets us up, how it teaches us, how we put ourselves in a better position to make a more perfect online world game,” said Phinney. “And that is, I think, exactly what Gronquist was talking about. There’s a depth to some of the systems that, sure, if we thought of it in terms of 'We’re trying to get people X many hours as a single-player game,' we wouldn't have needed to go into quite that level of depth, but because we’re looking at building systems that will extend [into Class 4], the side benefit is, as we’re working on it now, the variety we get out of the depth is really awesome.”

Edit: The original version of this article misspelled James Phinney's name. Ars Technica regrets the error.

Very cool, seems like something (nearly) the ultimate zombie-apocalypse game. A minor concern is that the open world simulation system might lead to too much homogeneity. That is to say, because zombies can be anywhere and everywhere, there might not be any location that offers especially interesting combat. It's often a problem with games that try for excessive dynamism or procedural generation. I hope not, but we'll see.

The game sounds interesting. I hope there is a way to turn off the game progressing when Im not playing. I have very little leisure time as is, and once I start school its going to drop to even less. Id hate to need to pass because I can only play an hour every 2 weeks.

There sure are an awful lot of zombie games being made these days. Not sure if want.

Agree. Zombies are quickly becoming the video game equivalent of those fad foods that start out in high-end restaurants and end up being advertised on the window stickers at McDonalds. (Sun-dried tomatoes or chipotle anyone?).

Fortunately the tech being described in the article (assuming it works as advertised) could quite easily be applied to a number of not-zombie games.

I enjoy zombie games and argue that you can't have too much of a good thing. No doubt there are some dud zombie games forthcoming, but there should be some good ones too. Hopefully this falls into the latter category.

The fact that the world evolves when you're not playing doesn't make sense without the MMO plans. Sure, you set things up for the other settlers to survive and grow, but your start is just going to hover over the trash can for three weeks while you vacation in Europe..

There sure are an awful lot of zombie games being made these days. Not sure if want.

Yeah, we're now getting into the second wave of zombie games. The first wave included things like Left 4 Dead. We finally had good enough graphics and processing power to actually model hordes of zombies, so the zombies behaved correctly. That was fun, but not what every zombie fanboy has been dreaming of.

That's what we're starting to get now with more "open world" zombie games like this, DayZ, and several others. Shooting tons of zombies is fun, but what we really want to know is if we could survive the zombie apocalypse. Can we scrounge supplies, learn how to deal with the zombies, and start to rebuild society.

Not sure if this game has the feature or not, but another classic element is that the zombies aren't the main threat, the other humans are.

This sort of emergent behaviour is exactly the type of thing I have always hoped from games like The Elder Scrolls series, XCom, GTA, etc. I always wonder why something like that hasn't been implemented yet when I see a new release (except the first two XCom games). Is it really that much harder than scripting the hell out of everything?

Emergent behaviour makes the playing experience so much more immersive and unique.

"This sort of emergent behaviour is exactly the type of thing I have always hoped from games like The Elder Scrolls series, XCom, GTA, etc."

... Same here!

As for if it's really that much harder - I think the answer is yes. The coding alone is more - but more importantly the planning and intelligence that must go into it is significantly greater than writing / executing hard-coded events. Is it so much harder as to not pay for itself? I don't think so - if you have a talented group of developers.

There sure are an awful lot of zombie games being made these days. Not sure if want.

Rewind 10 years or so ago....

"There sure are an awful lot of RTS games being made these days."

Developers are manufacturers, theyll pump out whats popular at the time....

Yeah, I'm a bit torn on this one myself. Personally, reading about the DayZ medics here on Ars brought me back into the fold of gaming a bit. I went out and purchased ARMAII/Arowhead just to load up the mod. I've been hooked ever since and am really waiting forward to the stand alone version. Other zombie games, not so much.

I do hope as the complexity of games continues to grow that more emergent behavior spawns out of them. That is what attracted me to DayZ. Sure, it was fun running for dear life at first and just surviving. I was delighted in some strange way just to find a can of beans. I played around with a couple Arsians for a while when the game got pretty popular but as things change, groups have left. It's pretty barren now. I've personally liked the lone wolf style of play, and now when I find some free time to goof off I wander the map, mostly at night. That or countersnipe bandits, hate bandits. Lately I've taken to helping people out in the cities by sniping Zeds with a .50 cal from as far off as feasable, normally around 1000m or so, just to help them out. But then I jet before someone comes around looking for my loot! I'm the helpful ghost from Chernarus I suppose, now that I think about it. What odd things we do from time to time.

As for if it's really that much harder - I think the answer is yes. The coding alone is more - but more importantly the planning and intelligence that must go into it is significantly greater than writing / executing hard-coded events.

This is what's wrong with most video games. If writing is easier than coding then your writing sucks.

The game sounds interesting. I hope there is a way to turn off the game progressing when Im not playing. I have very little leisure time as is, and once I start school its going to drop to even less. Id hate to need to pass because I can only play an hour every 2 weeks.

Agree...This game sounds intriguing, but an hour or two every other week is about all I likely find for games these days and nothing would turn me off from a game more than leaving it for 2 or 3 weeks and coming back to find that everything I'd done up to that point was essentially wiped out for no reason other than I hadn't played it in awhile.

The game sounds interesting. I hope there is a way to turn off the game progressing when Im not playing. I have very little leisure time as is, and once I start school its going to drop to even less. Id hate to need to pass because I can only play an hour every 2 weeks.

Agree...This game sounds intriguing, but an hour or two every other week is about all I likely find for games these days and nothing would turn me off from a game more than leaving it for 2 or 3 weeks and coming back to find that everything I'd done up to that point was essentially wiped out for no reason other than I hadn't played it in awhile.

I think they state in the article that if you leave the world in somewhat decent shape, it will remain so.

Is it common for zombies to lose their lower jaw and both their arms but nothing else? It sounds from this article that that happens on a regular basis (there's even a name for that particular type of zombie), but I'm having trouble imagining many scenarios where a dying or undead individual would suffer those three injuries but otherwise not be reduced to shreds or jelly...

Is it common for zombies to lose their lower jaw and both their arms but nothing else? It sounds from this article that that happens on a regular basis (there's even a name for that particular type of zombie), but I'm having trouble imagining many scenarios where a dying or undead individual would suffer those three injuries but otherwise not be reduced to shreds or jelly...

Is it common for zombies to lose their lower jaw and both their arms but nothing else? It sounds from this article that that happens on a regular basis (there's even a name for that particular type of zombie), but I'm having trouble imagining many scenarios where a dying or undead individual would suffer those three injuries but otherwise not be reduced to shreds or jelly...

Well, there appears to be quite a bit of chest trauma too in the forementioned zombie. I'm thinking that there may be a plethora of cherry flavored hand grenades modeled into the game. That might account for the observations. Just a guess.

I'm looking forward to this game, as I'm more interested in a thinking zombie game than another run and gun game. One of my favorite zombie movies is the old Dawn of the Dead. The whole idea of making a base and planning out is the most exciting part for me. Then after you set up the base, how to you manage resources, gather food/water, keep the security of the base from zombies, etc.

The fact that the world evolves when you're not playing doesn't make sense without the MMO plans. Sure, you set things up for the other settlers to survive and grow, but your start is just going to hover over the trash can for three weeks while you vacation in Europe..

It worked for Animal Crossing! (right?)

Anyway, sounds pretty neat. I'm not sure I want to bother with the XBLA version, but I would consider the PC (or PS3, but whatever). I, too, feel there's a little bit of zombie over saturation these days. If it's fun, it's fun, though.

I think they state in the article that if you leave the world in somewhat decent shape, it will remain so.

Yeah, but can you get the world into somewhat decent shape by playing an hour or two at a time would be my concern/question. Guess I'll have to wait for it to be released and hope for a review that covers that concern.

Not sure I'm really impressed by them saying they over-engineered the game, then talking about how 1 zombie can call hordes of others to it. A lot of games have some pretty crafty AI these days. What they described didn't sound "over-engineered" at all, just par for the course. (Or, at least, par for what players are expecting from a decent AI these days.)

The survival aspects do intrigue me more. Best zombie game I played was a flash game where you had to slowly expand out city-block by city-block and fortify your positions with medics, scavengers, etc. Occasionally, a horde would be spotted in the distance, and you had to prep for the assault. Was a great game, b/c it focused on the management of the apoc instead of the boots-on-the-ground direct fighting like L4D.

And, again, that simulation doesn't stop when you stop playing. “When you stop playing the game for the day, conceptually the world is still running,” Strain said. “When you start up the game, what we effectively do is look at the amount of time that’s elapsed and forward the simulation by that amount of time. We’re careful not to punish you for that

I really like the idea of the world evolving around me while I am in it, I do not like the idea that the amount I play the game will effect my playthrough. This would make sense in an MMO game, but for the single player game I think should not be the case. I hope at the very least they make it a setting that you can turn on/off.

A might be a little paranoid but this seems like a way to get people hooked in and always playing.

Not sure I'm really impressed by them saying they over-engineered the game, then talking about how 1 zombie can call hordes of others to it. A lot of games have some pretty crafty AI these days. What they described didn't sound "over-engineered" at all, just par for the course. (Or, at least, par for what players are expecting from a decent AI these days.)

I believe that the difference, in this case, is that the AI continues even while you are not around. What we think of as AI is typically only occurring in the area occupied by the character. Typically, if you're not in the room, the zombies are inactive, or at best, following much simpler roaming routines than what they do when the player is present. So, when they speak of being over-engineered, I believe they basically mean that they are trying to make the world behave as though the AI of all of the zombies is active all of the time, and this allows the world to change over time without the player's direct influence. Think of it as an approach to an open-world zombie game where the world is controlled by the computer like Sim City, rather than, say, Left 4 Dead.

As for the game itself, I don't know if I'm interested or not, as I've been getting a bit burned out on zombie games, but I like the concept, and would like to see it in a game like Skyrim. The zombie apocalypse is a good fit, though, because it is a progressive effect upon the world. Imagine if you neglected your duties as the Dragonborn, and the towns started getting progressively destroyed, because of the spread of dragons burninating everything. It obviously would take some fine tuning, and the game needs to be constructed with that in mind to get it right, but it's the kind of thing you can do with a lot of computing power at hand, and with a lot of up-front design so that you're not wasting all that simulation on a game that's no fun

Although I'm not a big fan of the zombie genre, I'm cautiously optimistic about this game. The open world survivor gameplay really appeals to me, and I saw promise in the demo they had at PAX. My main concern is how the PC controls work out, since that's where I'd want to play it, but it seems to be aimed more at consoles. I just hope they put enough effort into making PC-friendly controls and UI instead of the sham that most other console games do (I'm looking at you, Skyrim).

Is it common for zombies to lose their lower jaw and both their arms but nothing else? It sounds from this article that that happens on a regular basis (there's even a name for that particular type of zombie), but I'm having trouble imagining many scenarios where a dying or undead individual would suffer those three injuries but otherwise not be reduced to shreds or jelly...

Perhaps it can be considered a post-mortem injury that happens to many zombies for the same general reasons: They over-exert the soft tissue (muscle/tendon/skin) of their arms and jaws to the point that the joints fail and/or soft tissue gives away resulting in the loss of the limb or lower jaw.

This begs the question why their legs wouldn't also fail for similar "wear-releated" reasons but we're talking about re-animated corpses here so the "obvious" rules that govern bio-mechanics in our Zombies-Are-Impossible world probably don't apply in the Zombies-Are-Possilble world.

Is it common for zombies to lose their lower jaw and both their arms but nothing else? It sounds from this article that that happens on a regular basis (there's even a name for that particular type of zombie), but I'm having trouble imagining many scenarios where a dying or undead individual would suffer those three injuries but otherwise not be reduced to shreds or jelly...

Perhaps it can be considered a post-mortem injury that happens to many zombies for the same general reasons: They over-exert the soft tissue (muscle/tendon/skin) of their arms and jaws to the point that the joints fail and/or soft tissue gives away resulting in the loss of the limb or lower jaw.

This begs the question why their legs wouldn't also fail for similar "wear-releated" reasons but we're talking about re-animated corpses here so the "obvious" rules that govern bio-mechanics in our Zombies-Are-Impossible world probably don't apply in the Zombies-Are-Possilble world.

This right here. Zombies chew on everything and use their arms to do things we would never consider using them for (levers to pry doors open, clubs to beat on things, eating raw flesh and gnawing on bones) eventually these items fail because they are no longer be maintained and do not rejuvenate or repair themselves like living flesh. Undead flesh may not decompose (held in a state of "other" neither dead nor living) but it is susceptible to damage.

Sure, we might be a bit over saturated with zombie games, but zombies are the perfect cannon fodder for video games. Nazis, Terrorists, Orcs and Klingons are fun for a while, but eventually a gamer will have to face the fact that they're "people" too and don't deserve to be completely obliterated. Zombies don't get redeemed so they're more of a guilt free pleasure.

This sort of emergent behaviour is exactly the type of thing I have always hoped from games like The Elder Scrolls series, XCom, GTA, etc. I always wonder why something like that hasn't been implemented yet when I see a new release (except the first two XCom games). Is it really that much harder than scripting the hell out of everything?

Emergent behaviour makes the playing experience so much more immersive and unique.

The only vaguely similar thing I have encountered is awesome open source Elite remake, OOlite (http://www.oolite.org) The really nice thing is that all ships and other objects have powerful scripted behaviours (that can be modified by players ) and all of the game rolls on in a planetary system whether you take part or not. It's great.

Is it common for zombies to lose their lower jaw and both their arms but nothing else? It sounds from this article that that happens on a regular basis (there's even a name for that particular type of zombie), but I'm having trouble imagining many scenarios where a dying or undead individual would suffer those three injuries but otherwise not be reduced to shreds or jelly...

Perhaps it can be considered a post-mortem injury that happens to many zombies for the same general reasons: They over-exert the soft tissue (muscle/tendon/skin) of their arms and jaws to the point that the joints fail and/or soft tissue gives away resulting in the loss of the limb or lower jaw.

This begs the question why their legs wouldn't also fail for similar "wear-releated" reasons but we're talking about re-animated corpses here so the "obvious" rules that govern bio-mechanics in our Zombies-Are-Impossible world probably don't apply in the Zombies-Are-Possilble world.

This right here. Zombies chew on everything and use their arms to do things we would never consider using them for (levers to pry doors open, clubs to beat on things, eating raw flesh and gnawing on bones) eventually these items fail because they are no longer be maintained and do not rejuvenate or repair themselves like living flesh. Undead flesh may not decompose (held in a state of "other" neither dead nor living) but it is susceptible to damage.

Legs remain because they aren't receiving the same kind of abuse.

Zombies jaws and arms fail because when that fucker tries to eat me I am going to hack its arms and head with my hatchet.( And if you have played WarZ with me, you'll realise I am quite possibly the worst shot on the planet.)

In the zombie world, the head is the main target on a zombie. Makes sense that the face/jaw area will take signifigant damage. The arms are going to be second, as the clutching of feet by a zombie will cause you to react appropriately. Your gonna hack at the arms with whatever you have have available.